Conventionally known as an example of techniques relating to a spectrometer using a terahertz wave is a total reflection terahertz-wave spectrometer described in Patent Literature 1. In this total reflection terahertz-wave spectrometer, an entrance surface of an internal total reflection prism is integrally provided with a terahertz-wave generator, while an exit surface of the internal total reflection prism is integrally provided with a terahertz-wave detector. Using such an integral prism integrating the internal total reflection prism, terahertz-wave generator, and terahertz-wave detector together is advantageous in that it can detect the generation of terahertz waves at high efficiency while reducing the size of the total reflection spectrometer.